According to a CDC statistical brief, nearly 5.8 million people in the United States have congestive heart failure. See Lloyd-Jones D, et al. Heart Disease and Stroke Statistics-2010 Update. A Report from The American Heart Association Statistics Committee And Stroke Statistics Subcommittee. Circulation. 2010; 121:E1-E170. About 670,000 people are diagnosed with it each year. Heart failure was a contributing cause of 282,754 deaths in 2006. In 2010, heart failure cost the United States an estimated $39.2 billion. This total includes the cost of health care services, medications, and lost productivity.
Heart failure is a condition in which the heart's pumping power is weaker than normal. With heart failure, blood moves through the heart and body at a slower rate, and pressure in the heart increases. A delay between the contraction of the right and left ventricles often occurs with heart failure, so the walls of the left ventricle are unable to contract synchronously.
Approximately 25-50% of heart failure patients have ventricles that contract asynchronously, and are therefore candidates for biventricular pacing (between 1.5 and 3 million potential patients).
Biventricular pacing, also known as cardiac resynchronization therapy (CRT) utilizes a type of pacemaker that can pace both the septal and lateral walls of the left ventricle.1 By pacing both the right and left ventricles, the pacemaker can resynchronize a heart. 1 Pavia S V, Wilkoff B L. Biventricular pacing for heart failure. Cardiol Clin. 2001 November; 19(4):637-51.
Candidates for CRT include patients with severe or moderately severe heart failure symptoms, delayed electrical activation of the heart (such as intraventricular conduction delay or bundle branch block), or those with a history of cardiac arrest or risk factors for cardiac arrest.
CRT improves symptoms of heart failure in about one third of patients who have been treated maximally with medications but still have severe or moderately severe heart failure symptoms. Another third of patients see an improvement in ejection fraction without any major change in symptoms and the last third of the patient population are not responsive to CRT. CRT improves survival, quality of life, heart function, the ability to exercise, and helps decrease hospitalizations in select patients with severe or moderately severe heart failure. CRT can help improve ejection fraction (volume of blood pumped out of the left ventricle) and when combined with an implantable cardiac defibrillator, it can help protect against dangerous, fast heart rhythms.2 Both CRT pacemakers and CRT defibrillators use a left ventricular pacing lead. 2 Bristow M, et al. Cardiac-resynchronization therapy with or without an implantable defibrillator in advanced chronic heart failure. 2004. N Engl J Med 350 (21): 2140-50.
The CRT device and its leads can be implanted using an endocardial (transvenous) or epicardial (surgical) approach. The endocardial approach is the most common method. A local anesthetic is given to numb the area. The leads are inserted through an incision in the chest and into a vein. Two leads are guided to the right atrium and right ventricle of the heart, while the third lead is guided through the coronary sinus (the venous system of the heart) to the left ventricle. The lead tips are attached to the heart muscle, while the other ends of the leads are attached to the pacemaker placed in a pocket created under the skin in the upper chest. When the endocardial approach is used, the hospital recovery time is generally 24 hours. The endocardial technique is technically challenging. In some cases, this technique may not be successful due to the size, shape or location of the vein(s). If the endocardial approach cannot be used or is unsuccessful, the epicardial approach is then attempted.
The epicardial approach is a less common method in adults, but more common in children. The leads are placed under general anesthesia. The locations of lead placement are identical to the endocardial approach. The pulse generator is placed in a pocket created under the skin in the abdomen or chest. Although recovery with the epicardial approach is longer than that of the transvenous approach (generally about 3 to 5 days), minimally invasive techniques have enabled shorter hospital stays and recovery times.
There are several complications and costs associated with conventional pacing that may occur during biventricular pacing, including: (a) localized/skin infection, (b) systemic infection secondary to infected pacing box or lead, (c) bleeding, (d) hematoma, (e) lead displacement, (f) equipment failure, i.e. fractured pacing wire, faulty pacing box and (g) pneumothorax.
Standard predictors of operative complications apply, those being degree of heart failure, the surgical environment, diabetes and the duration of the procedure. Although with experience the procedure times reduce, even in the best hands implantation of the left ventricular lead may be time consuming, contributing to an increased infection risk.3 3 Alonso, C, et al. Six year experience of transvenous left ventricular lead implantation for permanent biventricular pacing in patients with advanced heart failure: technical aspects. Heart. 2001:86(4):405-410.
In the initial studies of biventricular pacing, the right atrial and right ventricular leads were inserted via the standard transvenous approach, but the epicardial left ventricular lead was placed surgically via thoracotomy or thoracoscopically. These approaches required a larger incision and general anaesthetic, consequently carrying a significant morbidity and mortality.
In 1998, the preferred method of left ventricular lead insertion using the transvenous approach was introduced.4 The precise location of the lead is ideally the mid left ventricular cavity in a lateral or posterolateral vein.5 The use of guiding catheters within the coronary sinus and the use of purpose-designed leads have increased success rates and ability to reach the target vessel. Some of these procedures may require the use of multiple types of catheters and guidewires, adding cost to this procedure. The requirement to position a lead in a branch of the coronary sinus and the techniques required to achieve this account for the additional complications and significant failure rate seen with biventricular pacing. A suitable vein may not be present in the lateral or posterolateral position, prompting placement of left ventricular lead in another ineffective suboptimal location. Thoracoscopic placement of left ventricular lead is not dependent on cardiac venous anatomy. Trans-cardiac-venous placement of left ventricular lead occasionally will cause disturbing phrenic nerve stimulation, causing uncomfortable diaphragmatic twitching and necessitate relocation to suboptimal sites. Thoracoscopic placement visualizes the phrenic nerve and thus placement away from the nerve can be accomplished at the outset. 4 Daubert, J C, et al. Permanent left ventricular pacing with transvenous leads inserted into the coronary veins. Pacing clin. Electrophysiol. 1998; 21(1 pt 2):239-245.5 Auricchio, A, et al. The pacing therapies for congestive heart failure (path-chf) study: rationale, design, and endpoints of a prospective randomized multicenter study. Am. J. Cardiol. 1999; 83(5b):130d-135d.
Although devices of various types have been developed for the endocardial approach, there remains a need for a device that is relatively simple to construct and use that permits firm and accurate lead or conduit placement in tissue, including cardiac tissue. There also are applications relating to a variety of operations and procedures involving the placement of a variety of leads or conduits in a variety of tissues that likewise would benefit from the device and methods of the present invention.